VEHICLE ON-BOARD WEIGHT INDICATOR

Abstract: A vehicle on-board weight indicator (10) comprising a converter means (11), an electrical signal receiving and processing means (12) and a numeric display (13). The electrical signal receiving and processing areas is typically a PLC although a specifically designed circuit can be employed. The converter means includes a first conversion stage comprising a linkage (14) connected at one end (15) to a fixed position relative to an axle (16) and at its other end (17) to a level actuator (18), the level actuator being secured to the vehicle chassis (not shown). The chassis is suspended above the axle (16) via a spring suspension (19) and as the vehicle is loaded, the distance between the axle (16) and the chassis changes according to the applied load.

Description: "VEHICLE ON-BOARD WEIGHT INDICATOR" FIELD OF THE INVENTION THIS INVENTION relates to a vehicle on-board weight indicator and in particular, but not limited to a weight indicator providing a display of weight distribution. BACKGROUND ART Transport vehicles are permitted by law to carry up to a maximum load per axle. A fine is incurred where a vehicle is overloaded. At present, on-board vehicle weight indicators are available but these are too expensive for most drivers. It is an object of the present invention to provide a less expensive alternative so that a driver can obtain an indication of overload so that he can elect to reduce or redistribute his load to avoid a fine. STATEMENT OF THE INVENTION In one aspect therefore, the present invention resides in a vehicle on¬ board weight indicator for a vehicle having relatively moveable parts displaceable in response to changes in the vehicle's load, movement of the parts providing a measurable displacement indicative of weight being carried by the vehicle, the on-board weight indicator comprising a converter means, an electrical signal receiving and processing means and a numeric display, the converter means being operative to convert the displacement between the relatively moveable parts to a displacement related electrical signal, the electrical signal receiver and processing means being adapted to receive the displacement related electrical signal and provide an output indicative of weight, and the numeric display means visually displaying weight information derived from said output from said electrical signal receiver and processing means. Preferably, a plurality of converters are employed at spaced apart locations on the vehicle, and each converter being operative to convert respective displacements between respective spaced pairs of relatively moveable parts so that a weight distribution can be displayed on the numeric display means. Typically, the relatively moveable parts comprise a chassis or part thereof and a wheel assembly or part thereof respectively. The displacement between the chassis relative to an axle as the chassis is loaded against an intermediate suspension is typically the displacement used by the present invention. Typically, a converter is employed adjacent each wheel and/or each axle of a vehicle so that a weight distribution across the vehicle can be obtained and displayed. A typical converter comprises first and second converter stages, the first converter stage is typically a mechanical displacement to liquid displacement conversion stage and the second conversion stage is typically a liquid displacement to electrical signal conversion stage. Preferably the converter means employs a differential pressure transducer. Where the converter involves displacement of a liquid by a mechanical means, a load reduction means is preferably employed to reduce load on the mechanical means when a measurement is not being taken. Preferably the load reduction means includes one or a pair of floating pistons. The floating piston(s) preferably communicate with a check valve and solenoid valve arranged in parallel so that liquid can flow away from the floating piston(s) when the solenoid valve is closed. The electrical receiver and processing means preferably includes calibration means so that the visual display gives a true indication of weight. The numeric display means typically displays weight information selected from the following:- (i) tare weight per axle; (ii) payload per axle; (iii) gross weight per axle; and (iv) gross weight of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS In order that the present invention can be more readily understood and be put into practical effect, reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention and wherein:- Figure 1 is a schematic view illustrating one preferred embodiment of a vehicle on-board weight indicator according to the present invention; Figure 2 is an alternative converter means suitable for use with the present invention; and Figures 3 to 7 are flow charts illustrating a typical control program suitable for a vehicle on board weight indicator according to the present invention. DESCRIPTION OF PREFERRED EMBODIMENT Referring to the drawings and initially to Figure 1, there is illustrated in schematic form a vehicle on-board weight indicator 10 comprising a converter means 1 1 , an electrical signal receiving and processing means 12 and a numeric display 13. The electrical signal receiving and processing areas is typically a PLC although a specifically designed circuit can be employed. The converter means includes a first conversion stage comprising a linkage 14 connected at one end 15 to a fixed position relative to an axle 16 and at its other end 17 to a level actuator 18, the level actuator being secured to the vehicle chassis (not shown). The chassis is suspended above the axle 16 via a spring suspension 19 and as the vehicle is loaded, the distance between the axle 16 and the chassis changes according to the applied load. The displacement between the axle and the chassis displaces liquid in the level actuator which forms part of a second conversion stage displacing liquid in an electronic fluid level indicator 20 to generate a displacement related electrical signal along line 21. An air pressure chamber 22 is employed to maintain pressure on the piston 18a of the level actuator 18. The displacement related electrical signal is then fed to the electrical signal receiving and processing means which has a plurality of inputs 23, 24 and 25 so that displacement related electrical signals from different locations on the vehicle can be input for processing. In the illustrated embodiment, the display is positioned in the driver's cabin and in this case, comprises a two column display with one display for a first axle being given generally at 26 and the other column being display for a second axle being given generally at 27. Extra displays would be used for extra axles. The first line in the display at column 26 and 27 would provide the tare weight per axle calculated from the input signals. The second line gives the payload per axle and the third line, the gross weight per axle. The lower display at 28 provides the gross weight of the vehicle also calculated from a sum of the input signals. Calibration knobs 29 are provided in order to calibrate the signal receiving and processing means so that a true weight indication is given on the display. A driver can easily check his approximate weight to sufficient accuracy so he can choose to reduce or redistribute his load to avoid a fine. So that the piston 27 is only under load when a measurement is being taken, an electrically actuated valve 26 is employed between the level actuator 18 and the level indicator 20. Referring now to Figure 2 there is illustrated an alternative converter means 28 based on a differential pressure transducer 29. A suitable transducer is marketed under the brand SMAR under the LD301 series available from SMAR International Corporation of Houston, Texas, U.S.A. A typical arrangement for a single axle is illustrated in Figure 2 where a pair of actuators 18 linked to the axles in the same general way as previously described. A separate arrangement of this type would be employed for each axle. A check valve 30 is employed to prevent fluid flow to the pistons 18 when the vehicle is moving. A solenoid valve 31 is employed and is opened when the vehicle is stationary and in order to take a measurement. A fluid column 33 shows the various load positions between no load and full load. The pistons 18 includes a floating piston 32 which is normally away from a piston seat 34 and as the check valve 30 only allows flow back up into the column 31 there will be no load on the axles until a reading is to be taken. When the solenoid valve 31 opens the floating pistons will seat on the seats 34 and a reading can be taken. Referring now to Figures 3 to 7 there is illustrated a typical program sequence applicable to the present invention. Figure 3 is the sequence in "off-line mode" where the system awaits an input from the keypad. The input can be say an F1 key to take a reading or a "page" key to display selected data or enter other operational modes including a "configuration mode". If the F1 key is struck the sequence of Figure 4 comes into play. The solenoid valve 31 opens and the floating pistons 32 seat on the seats 34 and then inputs are read out. Inputs can include a raw level input and a liquid temperature. These inputs are then processed to correct for temperature and to convert the raw level to display gross mass for the whole vehicle. Further key inputs can scroll through different data calculated say for each axle and sequentially display each one. Only a limited time is available for further action and once that time is up the system is deactivated and the solenoid valve closed. Figure 5 represents a sequence for display of stored values or limits following repeated striking of the "page" key. Once all limit values have been displayed the sequence leads into a "configuration mode" illustrated in Figures 6 and 7. The configuration mode prompts for a security code as actual limit values and operating parameters can be changed in this mode. It will be appreciated from the foregoing that the present invention has been illustrated schematically, for clarity and ease of understanding of the basic principles of the present invention. It will therefore be appreciated that whilst the above has been given by way of illustrative example of the present invention, many variations and modifications thereto will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as set forth in the appended claims.

Claims: CLAIMS 1. A vehicle on-board weight indicator for a vehicle having relatively moveable parts displaceable in response to changes in the vehicle's load, movement of the parts providing a measurable displacement indicative of weight being carried by the vehicle, the on-board weight indicator comprising a converter means, an electrical signal receiving and processing means and a display, the converter means being operative to convert the displacement between the relatively moveably parts to a displacement related electrical signal, the electrical signal receiver and processing means being adapted to receive the displacement related electrical signal and provide an output indicative of weight, and the display means visually displaying weight information derived from said output from said electrical signal receiver and processing means. 2. A vehicle on-board weight indicator according to claim 1 where a plurality of converters are employed at spaced apart locations on the vehicle to convert the displacement between the chassis relative to an axle as the chassis is loaded against an intermediate suspension. 3. A vehicle on-board weight indicator according to claim 1 or claim 2 wherein the converter comprises first and second converter stages, the first converter stage being a mechanical displacement to liquid displacement conversion stage and the second conversion stage being a liquid displacement to electrical signal conversion stage. 4. A vehicle on-board weight indicator according to claim 1 wherein the converter involves displacement of a liquid by a mechanical means, and includes a load reduction means employed to reduce load on the mechanical means when a measurement is not being taken. 5. A vehicle on-board weight indicator according to claim 1 wherein the electrical receiver and processing means includes calibration means so that the visual display gives a true indication of weight. 6. A vehicle on-board weight indicator according to claim 1 wherein the display means displays weight information selected from the following:- (i) tare weight per axle; (ii) payload per axle; (iii) gross weight per axle; and (iv) gross weight of the vehicle. 7. A vehicle on-board weight indicator according to claim 1 wherein the converter means employs a differential pressure transducer. 8. A vehicle on-board weight indicator according to claim 1 wherein the converter means includes a pair of floating pistons adapted to float to a position away from respective piston seats when the vehicle is moving. 9. A vehicle on-board weight indicator according to claim 3 wherein the liquid displacement to electrical signal conversion stage employs a differential pressure transducer. 10. A vehicle on-board weight indicator according to claim 4 wherein the load reduction means comprises a check valve in parallel with a solenoid valve both communicating with a floating piston so that liquid can flow away from the piston through the check valve when the solenoid is closed.

Inventors: MORRISON STEPHEN MAXWELL, MORRISON, STEPHEN, MAXWELL
Applicants: MORRISON STEPHEN MAXWELL, MORRISON, STEPHEN, MAXWELL
Application year: 1994
Main classification: B60P5
IPC codes: B60P5, G01G19